Moss Control in Container-Grown Conifer Seedlings
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Summer 1981/27 Moss Control in Container-Grown Conifer Seedlings William A. Haglund, Kenelm W. Russell, and Richard C. Holland Plant Pathologist, Cascade Agricultural Service Company, Mount Vernon, Wash.; and Forest Pathologist and Nursery Superintendent, Washington State Department of Natural Resources, Olympia on the surface of the growing sources container nursery in medium after sowing. The grit Bellingham. Eight commercially A combination of X77 surfactant may be applied at seeding or available surfactants were test- and Captan 50W controls moss later. To be effective, moss con- ed for moss control and in Douglas-fir, western hem - trol must be done at its first ap- phytotoxicity to Douglas -fir lock, or noble fir container pearance. The development of a (Pseudotsuga menziesii) and seedlings. Applications made selective chemical control for western hemlock (Tsuga on cool, cloudy days prevent moss that is safe for a wide heterophylla). Combinations of seedling injury. range of conifer species would surfactants and Captan 50W fun- provide an alternative to the gicide were also evaluated on grit, which is not always totally noble fir (Abies procera), west- successful. A chemical applica- ern hemlock, and Douglas -fir. Successful growing of green- tion would not only be more All of the treatments were ap- house container seedlings re- thorough, but also significantly plied as a spray to seedlings quires a highly skilled adher- cheaper than the grit from the growing in styroblock contain- ence to specific cultural labor standpoint. ers. Treatments were applied practices. Included in these The possibility that mosses with sufficient liquid either to practices is a rigorous disease might be selectively killed while wet the moss or to run off on control program. High humidi- leaving the seedling uninjured the seedling foliage. The rate of ties and optimum temperatures was discovered while routinely liquid applied varied with the in Pacific Northwest green- screening fungicides for control density of moss or size of houses allow rapid buildup and of damping off and other root seedling and was equivalent to 7 growth of a multitude of disease disease fungi. We found it nec- to 10 gallons of spray per 1,000 problems. essary first to wet an unusually square feet of treated area. Ob- Moss is one of the pests that thick crop of moss with a servations for phytotoxicity and can hinder container seedling surfactant to allow penetration degree of moss control were growth. Although not technical- by the fungicide and water car- made 7 and 14 days after treat- ly a "disease," excessive moss rier. We noted that, in some ment, and tree meas urements growth in the small cavities can cases, only 24 hours later the were taken 30 to 60 days after severely disrupt conifer wetting agent had killed back treatment. seedling growth in several ways. the moss. Further tests with Surfactants were tested at Moss can choke the very young drenches of a high rate of three rates of application: 2.5, seedling, causing stunting and Captan 50W mixed with 5.0, and 10.0 gallons per 100 gal- chlorosis by successfully surfactant for root diseases lons of water. Captan 50W was competing for nutrients and showed even better moss con- similarly added at 20, 40, and 80 light. A thick moss mat can pro- trol. The treatment appeared to pounds per 100 gallons of duce a water-repellent surface, desiccate the mosses complete- water. thus depriving the lower part of ly and rapidly. the cavity of its share of nutri- Results and Discussion ents and water. Materials and Methods X77 was the least phytotoxic To date, the most common A moss control test was estab- of the eight surfactants method of moss control has lished at the Washington State evaluated (table 1). Only three been to place coarse granite grit Department of Natural Re- wetting agents are shown be- 28/Tree Planters’ Notes Table 1.—Effects of three surfactants on the growth of Douglas-fir and shown in table 2, the applica- western hemlock 1 tion of X77 at the 2.5-gallon rate in combination with Captan 3 3 Westernhemlo ck Douglas-fir 50W was not phytotoxic to the Treatment2 Rate/100 gal/water Height Caliper Weight Height Caliper Weight seedlings, but when the X77 rate was increased to 10 gallons, X77 5 104 106 93 107 96 107 seedling phytotoxicity was ob- VWR 1 5 99 99 81 91 77 115 TrTad 5 84 86 81 103 77 75 served. Treatment with 10 gal- Control 0 100 100 100 100 100 100 lons X77 plus 80 pounds Captan X77 10 100 96 98 104 92 104 50W per 100 gallons was VWR 1 10 100 99 106 87 81 83 phytotoxic on the noble fir that Tryad 10 80 74 59 122 81 88 had some foliar injury before Control 0 100 100 100 100 100 100 treatment. 1Height, caliper, and weight are expressed as percentage of control, which is considered Application of the X77-Captan 100 percent. 50W combination to western 2X77 is a wetting agent from Chevron Chemical, Ortho Division. VWR 1 is a special hemlock seedlings under two wetting agent from Van Waters and Rogers, Inc. Tryad is a dispersant, activator, and greenhouse conditions demon- emulsifier from Kalo Laboratories, Inc. strated that the treatment can 3Data are based on four replications of 40 trees each. be very phytotoxic if applied under high-temperature condi- cause the others were too served in these tests. The X77 tions (table 3). Temperatures in phytotoxic to the seedling. Plant was used at 2.5 to 10 gallons per excess of 75° F combined with height, stem caliper, and total 100 gallons of water, and Captan sunshine may result in extreme weight of both Douglas -fir and 50W was added to this at 40 to phytotoxicity. Ninety-seven per- western hemlock seedlings 80 pounds per 100 gallons. cent of the western hemlock were not significantly reduced No phytoxicity was observed seedlings treated at 80°F with by X77. The data are based on when the optimum rates (2.5 to sunshine were injured, while no one application with measure- 5 gal X77 plus 40 to 80 lb Captan injury was observed when treat- ments made 60 days later. A lat- 50W/100 gal water) were used ments were applied in a normal- er similar test with X77 plus and applied under ideal weather ly cool greenhouse (table 3). Captan 50W was made in the conditions. Control of 95 per- department's Olympia res earch cent indicates that after 30 days Conclusions greenhouse. Results were the the moss was brown and no re- Applications of X77 and same. growth was visible. We noted Captan 50W in experimental Virtually complete moss con- some regrowth of the moss aft- and limited commercial trials trol was achieved when Captan er 30 days in treatments where it have demonstrated that virtually 50W was combined with X77 had been unusually thick or complete control of moss can and applied to western hemlock nearly mature. be obtained. We recommend and noble fir styroblock-grown Two lots of noble fir were the following application rates seedlings. Tables 2 and 3 pre- treated—one in which the trees and precautions: Douglas -fir, sent examples of the types of had previous foliar damage and western hemlock, and noble fir control and phytoxicity ob- one appearing normal. As do not show phytotoxicity fol- Summer 1981/29 Table 2.—E ffects of combinations of Captan and X77 on noble fir1 lowing applications of 2.5 to 5 gallons of X77 plus 40 to 80 Application rate/100 gal/water pounds of Captan 50W per 100 Tree3 Moss4 gallons of water. Increasing X77 Captan2 X77 injury control to 10 gallons per 100 gallons of water will cause seedling lb gal % % phytotoxicity. Twenty pounds of A. 0 0 20 0 Captan per 100 gallons of water 0 2.5 15 5 may be marginal for moss con- 80 2.5 15 95 trol and over 80 pounds may 80 10.0 8 95 cause seedling phytotoxicity. B. 0 0 0 0 Nursery workers should spray 40 2.5 0 95 sufficiently to wet the moss 80 2.5 0 95 thoroughly or to the point of 40 10.0 3 95 run-off on seedling needles. 80 10.0 0 95 Application in this manner will 1Trees in group A had prior foliar injury. Trees in group B had little or no prior injury. result in 7 to 10 gallons of chem- 2Captan 50W is a wettable powder fungicide (Ortho). icals per 1,000 square feet of 3Tree injury is the percentage of seedlings within each treatment with foliar injury, but is treated area. Applications not necessarily related to treatment. should not be made in sunlight 4Under moss control, 95-percent lull or control indicates that the moss was brown and no or when greenhouse tempera- regrowth was observed 60 days after treatment. tures are over 75° F. We suggest spraying in the late afternoon on a cloudy day. Table 3.—E ffects of temperature on the degree of phytotoxicity to Control results will be best western hemlock seedlings caused by combinations of X77 and when moss is treated while it is Captan still small, instead of waiting for thick moss mats to develop. In Rate/100 gal/water Greenhouse temperature thicker mats, regrowth may oc- 60-65° F 80-90° F cur following treatment. One or more repeat applications at 2- 1 2 Tree Moss Tree Moss or 3-week intervals may be nec- Captan X77 injury control injury control essary to achieve satisfactory lb gal.